1. Field
The present invention relates generally to telecommunications, and, more specifically, the invention relates to wireless communication systems and cellular communication systems.
2. Background
A modern communication system is expected to provide reliable data transmission for a variety of applications, such as voice and data applications. In a point-to-multipoint communications context, known communication systems are based on frequency division multiple access (FDMA), time division multiple access (TDMA), code division multiple access (CDMA), and perhaps other multiple access communication schemes.
A CDMA system may be designed to support one or more CDMA standards, such as (1) the “TIA/EIA-95 Mobile Station-Base Station Compatibility Standard for Dual-Mode Wideband Spread Spectrum Cellular System” (this standard with its enhanced revisions A and B may be referred to as the “IS-95 standard”), (2) the “TIA/EIA-98-C Recommended Minimum Standard for Dual-Mode Wideband Spread Spectrum Cellular Mobile Station” (the “IS-98 standard”), (3) the standard sponsored by a consortium named “3rd Generation Partnership Project” (3GPP) and embodied in a set of documents known as the “W-CDMA standard,” (4) the standard sponsored by a consortium named “3rd Generation Partnership Project 2” (3GPP2) and embodied in a set of documents including “TR-45.5 Physical Layer Standard for cdma2000 Spread Spectrum Systems,” the “C.S0005-A Upper Layer (Layer 3) Signaling Standard for cdma2000 Spread Spectrum Systems,” and the “TIA/EIA/IS-856 cdma2000 High Rate Packet Data Air Interface Specification” (the “cdma2000 standard” collectively), (5) the 1xEV-DO standard, and (6) certain other standards. The standards expressly listed above are incorporated by reference as if fully set forth herein, including annexes, appendices, and other attachments.
Data-only and data-optimized or “DO” cellular communication systems have been developed to satisfy the constantly increasing demand for wireless data services. As the name implies, DO systems are optimized for data transmission (as opposed to voice transmission), and in particular such systems are optimized for downlink data transmission. Data-optimized systems need not exclude uplink data transmission, or voice transmission in either direction. It should be noted that voice may be transmitted as data, for example, in the case of voice over internet protocol (VoIP) transmissions.
In wireless networks, an access terminal configured for communication may be in a traffic state/mode or in a dormant state/mode. In the traffic state, air link resources for communication between the access terminal and the radio network are allocated at the radio network and powered on at the access terminal. Air link resources at the access terminal may include, for example, finger resources and channel elements. In the dormant state, the traffic channel is torn down, and air link resources are powered off at the access terminal. Power required for operating these resources is consequently not spent during the dormant state, and battery life at the access terminal is extended. Other subsystems of the access terminal may also be powered off or put into a power saving mode for most of the time during the dormant state; the access terminal then wakes up every so often to listen to the paging channel of the wireless system, in order to respond to the incoming pages or communication requests. The duty cycle of such periodic paging channel checks is low, to reduce the stand-by power consumption.
For a given battery capacity, power consumption determines the amount of time that the access terminal can operate without recharging. Conversely, for a specified operating time between recharging the battery, average power consumption determines the required battery capacity and, consequently, the size, weight, and cost of the battery. Reducing power consumption of an access terminal is thus quite important.
Because transmissions from a given access terminal are interference for transmissions from other access terminals, it is also desirable to reduce the duration and/or power levels of such transmissions.
Therefore, there is a need in the art for methods and apparatus that would reduce power consumption and interference of access terminals. There is also a need in the art for methods and apparatus for reducing power consumption and interference of the access terminals without excessively compromising performance characteristics of the access terminals and of the radio networks with which the terminals communicate. There is a further need for methods of upgrading previously-deployed networks to provide for reduced access terminal power consumption and interference, while at the same time maintaining backward compatibility with legacy access terminals, and minimizing or eliminating hardware changes to the radio network.